Prepare. Preheat your oven to 350 and prep your muffin pan for nonstick.
Dry Ingredients. In a medium bowl, use a whisk to combine together your flour, baking soda, and salt.
Sugar. Next, in a large mixing bowl, beat together your sugar and oil until smooth and creamy.
Wet Ingredients. Add the mashed bananas, milk, vanilla extract, and egg to the mixing bowl and mix until combined.
Transfer. Use a cookie scoop or similar item to scoop the batter into your prepared muffin cups, filling them about three quarters of the way full.
Spread. Use a tablespoon to place dollops of the hazelnut spread on top of each of the muffins. Then use a toothpick, or similar item, to swirl the spread throughout the muffins, without over-mixing the muffins.
Bake. Bake your muffins for 18-20 minutes or until the tops are firm and begin to brown.
Cool. Let your muffins sit in the pan for 5 minutes before transferring them to cooling rack to fully cool.